Tantei Xeno to Nanatsu no Satsujin Misshitsu

Detective Xeno, who after being found collapsed at the side of a road covered in blood, was taken to a hospital. The first thing he did upon awakening was solving a murder that happened in the hospital! Xeno himself has no memory of who he is or where he came from, but after that huge incident and leaving the hospital, he opened up a detective agency. In just a year, he has solved some high-profile cases.